In the past, molds were mounted on a beam having a length corresponding to the radius of curvature and pivoted at the centre of curvature. The mold was mounted on the other end of the beam and moved with the beam during oscillation. The rather long beam length involved and many mechanical difficulties encountered with changes in beam length, fatigue, and load on the bearings were found to be impractical.
The aforementioned problems were at least parts addressed by the adoption of short levers provided in pairs and connecting the mold to an external support disposed between the mold and the centre of curvature. The short levers were inclined relative to each other and aligned to the centre of the casting arc. This improvement in the art is well described in U.S. Pat. No. 3,343,592 to Vogel. Because the reciprocating movement of the mold is very short (0.050 to 0.5 in) the deviation of the short lever travel from the casting arc is very small and the mold movement along the casting radius is acceptable. However, the pin joints of this design introduce some undesirable clearances which have to be carefully controlled to make the method practical. The operating conditions of a casting plant, including extremely high temperatures, moisture, and abrasive substances in the atmosphere make the oscillator highly maintenance intensive.
In U.S. Pat. No. 4,456,052 to Takashi Kawakami, the short lever design is improved by introducing a hydraulic cylinder which compensates for bearing clearances.
The present tendency is to increase the frequency of continuous casting molds and permit frequencies of up to 400 cylces per minute. This requirement has lead to completely new designs using a multitude of eccentrics as in U.S. Pat. No. 4,480,678 to Cazaux et al. While this is an improvement, it is a high cost mechanically complex apparatus requiring carefully controlled maintenance. Some proposals have been made to use leaf springs in this field, as in U.S. Pat. No. 3,664,409 to Kolomeitsev et al and DE 3 000 117 to Sack, these springs are disposed in a manner which subjects them to both compressive and tensile forces. They are thus limited in their application to situations where the buckling load of the leaf spring cannot be exceeded and thus are of limited use.
The object of this invention is to address the aforementioned problems described with reference to the prior art, namely to simplify the construction of the mold oscillator and to produce a high frequency oscillation which is stable and maintenance free.